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Diffstat (limited to 'src/tun/tun.c')
| -rw-r--r-- | src/tun/tun.c | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/src/tun/tun.c b/src/tun/tun.c new file mode 100644 index 0000000..3b0e9b9 --- /dev/null +++ b/src/tun/tun.c @@ -0,0 +1,271 @@ +/* + This file is part of GNUnet. + (C) 2010, 2011, 2012 Christian Grothoff + + GNUnet is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published + by the Free Software Foundation; either version 3, or (at your + option) any later version. + + GNUnet is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received a copy of the GNU General Public License + along with GNUnet; see the file COPYING. If not, write to the + Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. +*/ + +/** + * @file tun/tun.c + * @brief standard IP calculations for TUN interaction + * @author Philipp Toelke + * @author Christian Grothoff + */ +#include "platform.h" +#include "gnunet_tun_lib.h" + +/** + * IP TTL we use for packets that we assemble (8 bit unsigned integer) + */ +#define FRESH_TTL 64 + + +/** + * Initialize an IPv4 header. + * + * @param ip header to initialize + * @param protocol protocol to use (i.e. IPPROTO_UDP) + * @param payload_length number of bytes of payload that follow (excluding IPv4 header) + * @param src source IP address to use + * @param dst destination IP address to use + */ +void +GNUNET_TUN_initialize_ipv4_header (struct GNUNET_TUN_IPv4Header *ip, + uint8_t protocol, + uint16_t payload_length, + const struct in_addr *src, + const struct in_addr *dst) +{ + GNUNET_assert (20 == sizeof (struct GNUNET_TUN_IPv4Header)); + GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv4Header)); + memset (ip, 0, sizeof (struct GNUNET_TUN_IPv4Header)); + ip->header_length = sizeof (struct GNUNET_TUN_IPv4Header) / 4; + ip->version = 4; + ip->total_length = htons (sizeof (struct GNUNET_TUN_IPv4Header) + payload_length); + ip->identification = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, + 65536); + ip->ttl = FRESH_TTL; + ip->protocol = protocol; + ip->source_address = *src; + ip->destination_address = *dst; + ip->checksum = GNUNET_CRYPTO_crc16_n (ip, sizeof (struct GNUNET_TUN_IPv4Header)); +} + + +/** + * Initialize an IPv6 header. + * + * @param ip header to initialize + * @param protocol protocol to use (i.e. IPPROTO_UDP), technically "next_header" for IPv6 + * @param payload_length number of bytes of payload that follow (excluding IPv4 header) + * @param src source IP address to use + * @param dst destination IP address to use + */ +void +GNUNET_TUN_initialize_ipv6_header (struct GNUNET_TUN_IPv6Header *ip, + uint8_t protocol, + uint16_t payload_length, + const struct in6_addr *src, + const struct in6_addr *dst) +{ + GNUNET_assert (40 == sizeof (struct GNUNET_TUN_IPv6Header)); + GNUNET_assert (payload_length <= UINT16_MAX - sizeof (struct GNUNET_TUN_IPv6Header)); + memset (ip, 0, sizeof (struct GNUNET_TUN_IPv6Header)); + ip->version = 6; + ip->next_header = protocol; + ip->payload_length = htons ((uint16_t) payload_length); + ip->hop_limit = FRESH_TTL; + ip->destination_address = *dst; + ip->source_address = *src; +} + + +/** + * Calculate IPv4 TCP checksum. + * + * @param ip ipv4 header fully initialized + * @param tcp TCP header (initialized except for CRC) + * @param payload the TCP payload + * @param payload_length number of bytes of TCP payload + */ +void +GNUNET_TUN_calculate_tcp4_checksum (const struct GNUNET_TUN_IPv4Header *ip, + struct GNUNET_TUN_TcpHeader *tcp, + const void *payload, + uint16_t payload_length) +{ + uint32_t sum; + uint16_t tmp; + + GNUNET_assert (20 == sizeof (struct GNUNET_TUN_TcpHeader)); + GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_TcpHeader) == + ntohs (ip->total_length)); + GNUNET_assert (IPPROTO_TCP == ip->protocol); + + tcp->crc = 0; + sum = GNUNET_CRYPTO_crc16_step (0, + &ip->source_address, + sizeof (struct in_addr) * 2); + tmp = htons (IPPROTO_TCP); + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t)); + tmp = htons (payload_length + sizeof (struct GNUNET_TUN_TcpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint16_t)); + sum = GNUNET_CRYPTO_crc16_step (sum, tcp, sizeof (struct GNUNET_TUN_TcpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length); + tcp->crc = GNUNET_CRYPTO_crc16_finish (sum); +} + + +/** + * Calculate IPv6 TCP checksum. + * + * @param ip ipv6 header fully initialized + * @param tcp header (initialized except for CRC) + * @param payload the TCP payload + * @param payload_length number of bytes of TCP payload + */ +void +GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip, + struct GNUNET_TUN_TcpHeader *tcp, + const void *payload, + uint16_t payload_length) +{ + uint32_t sum; + uint32_t tmp; + + GNUNET_assert (20 == sizeof (struct GNUNET_TUN_TcpHeader)); + GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_TcpHeader) == + ntohs (ip->payload_length)); + GNUNET_assert (IPPROTO_TCP == ip->next_header); + tcp->crc = 0; + sum = GNUNET_CRYPTO_crc16_step (0, &ip->source_address, 2 * sizeof (struct in6_addr)); + tmp = htonl (sizeof (struct GNUNET_TUN_TcpHeader) + payload_length); + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t)); + tmp = htonl (IPPROTO_TCP); + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t)); + sum = GNUNET_CRYPTO_crc16_step (sum, tcp, + sizeof (struct GNUNET_TUN_TcpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length); + tcp->crc = GNUNET_CRYPTO_crc16_finish (sum); +} + + +/** + * Calculate IPv4 UDP checksum. + * + * @param ip ipv4 header fully initialized + * @param udp UDP header (initialized except for CRC) + * @param payload the UDP payload + * @param payload_length number of bytes of UDP payload + */ +void +GNUNET_TUN_calculate_udp4_checksum (const struct GNUNET_TUN_IPv4Header *ip, + struct GNUNET_TUN_UdpHeader *udp, + const void *payload, + uint16_t payload_length) +{ + uint32_t sum; + uint16_t tmp; + + GNUNET_assert (8 == sizeof (struct GNUNET_TUN_UdpHeader)); + GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_IPv4Header) + sizeof (struct GNUNET_TUN_UdpHeader) == + ntohs (ip->total_length)); + GNUNET_assert (IPPROTO_UDP == ip->protocol); + + udp->crc = 0; /* technically optional, but we calculate it anyway, just to be sure */ + sum = GNUNET_CRYPTO_crc16_step (0, + &ip->source_address, + sizeof (struct in_addr) * 2); + tmp = htons (IPPROTO_UDP); + sum = GNUNET_CRYPTO_crc16_step (sum, + &tmp, + sizeof (uint16_t)); + tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length); + sum = GNUNET_CRYPTO_crc16_step (sum, + &tmp, + sizeof (uint16_t)); + sum = GNUNET_CRYPTO_crc16_step (sum, + udp, + sizeof (struct GNUNET_TUN_UdpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, + payload, + payload_length); + udp->crc = GNUNET_CRYPTO_crc16_finish (sum); +} + + +/** + * Calculate IPv6 UDP checksum. + * + * @param ip ipv6 header fully initialized + * @param udp UDP header (initialized except for CRC) + * @param payload the UDP payload + * @param payload_length number of bytes of UDP payload + */ +void +GNUNET_TUN_calculate_udp6_checksum (const struct GNUNET_TUN_IPv6Header *ip, + struct GNUNET_TUN_UdpHeader *udp, + const void *payload, + uint16_t payload_length) +{ + uint32_t sum; + uint32_t tmp; + + GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) == + ntohs (ip->payload_length)); + GNUNET_assert (payload_length + sizeof (struct GNUNET_TUN_UdpHeader) == + ntohs (udp->len)); + GNUNET_assert (IPPROTO_UDP == ip->next_header); + + udp->crc = 0; + sum = GNUNET_CRYPTO_crc16_step (0, + &ip->source_address, + sizeof (struct in6_addr) * 2); + tmp = htons (sizeof (struct GNUNET_TUN_UdpHeader) + payload_length); /* aka udp->len */ + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t)); + tmp = htons (ip->next_header); + sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof (uint32_t)); + sum = GNUNET_CRYPTO_crc16_step (sum, udp, sizeof (struct GNUNET_TUN_UdpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length); + udp->crc = GNUNET_CRYPTO_crc16_finish (sum); +} + + +/** + * Calculate ICMP checksum. + * + * @param icmp IMCP header (initialized except for CRC) + * @param payload the ICMP payload + * @param payload_length number of bytes of ICMP payload + */ +void +GNUNET_TUN_calculate_icmp_checksum (struct GNUNET_TUN_IcmpHeader *icmp, + const void *payload, + uint16_t payload_length) +{ + uint32_t sum; + + GNUNET_assert (8 == sizeof (struct GNUNET_TUN_IcmpHeader)); + icmp->crc = 0; + sum = GNUNET_CRYPTO_crc16_step (0, + icmp, + sizeof (struct GNUNET_TUN_IcmpHeader)); + sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length); + icmp->crc = GNUNET_CRYPTO_crc16_finish (sum); +} + + +/* end of tun.c */ |